The present invention relates to an apparatus for monitoring the degree of compaction achieved by mobile soil compacting devices of the type including at least one vibrating compacting tool, wherein a measured value which has a known relationship to the effective power of the vibratory compacting tool is sensed and stored as a measure for the degree of compaction.
U.S. Pat. No. 4,127,351 discloses the use, instead of physical characteristics of the soil itself, of a value which can be measured directly at the compacting device as an indication of the effective power actually applied to the soil as well as indication of the actual degree of compaction imparted to the soil. Any value which has a fixed relationship to the effective power of the compacting tool can be used as such a parameter, for example the driving power of the compacting tool minus the reactive power component consumed within the system itself, i.e. in hydraulically driven compacting tools the hydraulic pressure minus the pressure component consumed as reactive power. In compacting systems employing a plurality of independently operated compacting tools, the soil settlement derived from the difference in height of the individual tools is particularly suitable.
These measured values have been found to be very satisfactory in the determination of the amplitude variation in the sense of maximum compacting performance as disclosed in the above-mentioned patent. However, in a number of compacting devices measurement of these values often does not permit accurate conclusions to be drawn regarding the corresponding actual degree of compaction of the soil so that it cannot be determined whether it would be worthwhile to perform further passes with the compacting device or whether such passes would be superfluous or even result in renewed loosening of the soil at the surface.